Erwin kramer



Aug. 17 1926.

E". KRAMER FEEDING MECHANISM FOR MILLS' Filed Nov'. s, i925 2 Sheets-Sheet 1 Aug. 17, 1926.

, IF'EEDINGv MECHANISM FOR MILLS 'Filed Nov. s. 192,5l f 2 shun-shut 2 1,596,051I E. KRAMER Patented Aug. 17, 1926,

UNITED STATES PATENT OFFICE.

ERWIN KRAMER, OF BERLIN, GERMANY.

FEEDING MECHANISM FOR MILLS.

Application filed November 3. 1925, Serial No. 66.506, and in Germany Uctober 31,1924.

This invention relates in general to mills, more-particularly to eddy mills of the kind described in the copeiidiiig patent application. Serial No. 735,253. An important factor in continuously-operatiiig mills of this kind is the rate at which the material to be lground is fed into the mill, because the efficicncy of the mill depends upon this factor in a high degree. lf the mill is not sufficiently filled a considerable quantity of energy is consumed for producing the cddies without a corresponding amount of useful Work being donc. On the other hand if too much material is fed into the mill, the generation of eddies is interfered with, and the proper colliding of the particles of material against each other prevented.

When the material to be ground has a high specific weight, as in the case of metal., these evils are apt to result in an excessive deposit of metal in the mill and to cause breakages of the driving mechanism, etc.

The poiver required for driving the eddy mill differs according to the quantity of material fed in` to the size of the granules and to the specific weight of the same. The toughness-and other properties of the material also have a considerable effect. It has been found by experiment that the power required as measured at the driving shafts depends on the kind of material treated, the size of its granules and the rate ofl feed, and that the greatest economy is obtained when the rate of fecdis regulated so that the amount of Work performed at the driving shafts remains constant.

This object is not accomplished when the ordinary feed devices such as feeding Worms, vvheels, buckets or the like, that are moved at a constant speed, are employed, unless the material to be ground is carefully sorted before it is introduced into the mill.

ln accordance with the present invention the material to be ground is fed into the mill or disintegrator in such a manner that the strength of the torque to be applied to the driven shafts is maintained practically constant.

This is accomplished by controlling the torque at the driving shaft with the aid of the devices hereinafter described and. by causing material to be fed into the mill Whenever the torque sinks beneath a certain strength until the torque is again increased to normal. The feeding device is then put out of operation and only started again when the torque sinks to a certain degree. By this meansthe strength of the torque can be maintained constant Within narrow limits.

The advantages that accrue from such an arrangement are the following:

The size of the granules of the material to be ground may differ very greatly without necessitating any change of the adjustment of the mill. Furthermore different kinds of material can be fed into the mill without altering the same and mixtures of entirely different kinds of material can be ground in the mill simultaneously. The driving power and capacity of the mill are fully utilized throughout the entire time of operation of the mill and overloading of the same, which results in a reduction of its efficiency and may lead to mechanical injuries of the mill or its power machine, is obviated.

Then the mill is driven by electric motors the torque applied is measured in terms of the strength of the current consumed by the motor or motors. In the case of a mechanical drive through cogwheels, sprockets, belts or the like, the torque applied is measured by the degree of fleXure of an elastic member arranged in the driving mechanism.

The invention is illustrated by Way of example in the drawing in which Figure 1 is a vertical section of the automatic feeding device and a side elevation of the mill and of parts of electric motors driving the mill.

Figure 2 is a vertical section of the feeding device taken on the line A, B, C, D, at right angles to the section shown in Figure 1.

Figure 8 shows a longitudinal and a transverse section of a mechanicaldevice for controlling the torque, and Figure 4 shovvs an electrical torqiie-controlling device.

Referring to Figure 1, the material to be ground is filled into a container or hopper 1 and passes down from the same into a trough 3 which is adapted to be vibrated When necessary to the right and left as indicated by the arrou7 54. By this means the material is assed on in proper quantities, i. e. slides rom the trough '3 and drops down in the chamber 9 which envelops the troughv and then passes through a connecting pipe 11 into the casing 55 of the mill Whose shafts 56 and 57 are rotated by the electric motors 58 and 59. The rate at which K project from a recess 4 the chamber 9. The

shaft 8 has fixed upon it a forked arm 7 the clutch member the material is fed into the mill thus de- Eends on the rate of movement of the virating trough 3. This trough is supported at its left end by a roll 4. At its other end the trough is provided with an axis 5 that is adapted to be oscillated by an arm 6 pivoted at 8. The two ends of the shaft 8 18 in the sloping wall of the chamber 9 into this chamber, i. e. the middle part of the shaft 8 is located in a second'chamber 10 which is integral with middle part of the whose prongs engage with a cam 12 fixed on a shaft 13. The shaft 13, which is pivoted in the chamber 10, is rotated continuously by a pulley in any desired manner. Keyed on the shaft 13 is a clutch member 14 whose projecting teeth 15 are adapted to engage with a corresponding number of teeth 16 which project from the cam 12. The cam 12 is arranged to slide to and tro on the shaft 13. A spring 17 normally presses the cam 12 with its teeth 16 away from the clutch member 14, as shown in Figure 2. Whenever the cam 12 is pressed against the coupling member 14 it is rotated by the shaft 13 so as to oscillate the fork 7 and the arm 6 and consequently also the vibrating trough 3, which causes material to drop into the mill as long as it vibrates.

The shifting of the cam 12 along the shaft 13 can be accomplished in various ways. As shown in Figure 2 an electromagnet 20 may e used for this purpose. When this magnet is energized it attracts its armature 23 which is normally lifted as shown by a spring 24. On the attraction of the armature it swings on its pivot 22 and forces the arm 21 against the cam 12, thus pushing the latter towards the left until its projections 16 engage with the teeth 15 so that it rotates and oscillates the vibrating trough.

netic contact closer whose windings are connected in the circuit of the one electric motor 58 or the other 59. As long as the torque. and hence the current in the motor Figure 4. Hence the feeding device 3 operates until the torque of the motor and consequently also the motor current rises to a certain de- As soon as this happens the relay opens the energizing circuit of the magnet the cam 12 out of engagement with 14 so as to stop the operation of the trough 3 and the feeding of material into the mill. As the grinding of as shown by way of example ling the shaft 25 the material proceeds and the ground material passes out of the mill the torque exerted by the motor decreases and this is accompanied by a decrease of the motor current. The relay 38 then releases its armature and the energizing current of the magnet 20 is again switched on to throw on the clutch. The aforedescribed events are then repeated, i. e. material is fed into the mill again until the motor current increases to a given strength.

The arrangement ot'. and the control effected by, the aforesaid relay are shown diagrammatically in Figure 4. The limbs 39 and 49 of the horse-shoe electromagnet 38 are provided with coils 4l and 42 which are connected in the circuit of the motor. A lever 45 pivoted at 44 carries an armature 43 and a contact spring 46. A spring 52 pulls the lever 45 upwards. tion a current Hows from the battery 48 through a conductor 50, the lever 45. the contact spring 46, the Contact anvil 47 and thence through the coil 49 of the magnet 20 back to the battery 48. ll'hen the magnet 38 is energized sullicicntly to pull the armature 43 down against the action of the spring 52, the contact spring 46 is removed from the contact anvil 47 and strikes against the stop 51. The current in the coil 49 of the magnet 20 is thus interrupted so that the magnet 20 is deenergized. The arrangement of the clutch may, of course. be modified so that the spring 17 normallyv presses thecam 12 into engagement with the clutch member 14 and the electromagnet 29 shifts the cam 12 towards the right when it is energized. i. e. it throws the couplingr off instead of on. With this arrangement the right hand end of the coil 49 is connected to the contact anvil 51, instead of the anvil 47. and when the magnet 38 is energized sutliciently the armature 43 is attracted and the circuit of the coil 49 is closed, so that the electromagnet 20 disengages the cam 12 from the clutch member 14. Thus, when the strength of the motor current sinks to a cer- 'tain degree, the electromagnet 38 releases the armature 43 to interrupt the current in the coil 49 and the cam 12 engages with the coupling 14 and the feeding device then feeds material into the mill until the current in the electromagnet 38 rises to such an extent that it again attracts its armature 43.

Instead of controlling the torque at the shaft of the mill by electrical means. a mechanical controlling means may be used in the lower part of Figure 2 and in Figure 3. In this driving means a pulley 30 is used `tor drivof the mill. Tnstead of the pulley 30. any other desirable driving member such as a coupling, cogwhecl or the like may be used. The pulley 30 is arcause the pulley ranged to turn relatively to thel shaft 25 on which is keyed a coupling member 26 with projections 27 that are adapted4 to cooperate with projections 28 fixed to the pulley 30. Between each pair of cooperating projections 27 and 28 is arranged a pressure spring 29. In driving the mill the pulleySO coinpresses the spring 29 to a lesser or greater extent according as the shaft 25 oll'ers a greater or lesser resistance. Hence according as the resistance to be overcome, or the torque to be exerted, is small`or great, a greater or lesser rotation of the pulley7 30 relatively to the shaft 25 takes place. This relative rotary movement is used to effect a lateral displacement of a controlling disk 3l. To this end a male screw 32 is fixed to the end of the shaft 25 which is received by a female screw in the disk 31. The ydisk 31 has a pin 33 which enters into a hoe in the hub of the pulley 30, so that the disk 31 rotates with the pulley 30. Whenever the pulley 30 rotates relatively to the shaft 25 the disk 31 is caused to shift to the right or left by the agency of the screw 32. A two-arm lever 35 and 36, which is pivoted at 34, engages at its lower end with a groove in the periphery of the disk 31. As long as the disk 31 revolves without executing any lateral movement the lever 35, 36 remains stationary, but when the disk 31 is shifted towards the right the lever 35 swings to the right and the arm 36 is pressed to the lcft so that it forces the cam 12 against the couling member 14 by means of the rod 37.

he cam 12 is thus caused to rotate with the shaft 13 and to start the operation of the trough. WV hen the disk 31 returns to its original position the rod 37 shifts to the right to allow the cam 12 to disengage and stop the feeding operation. l

When `the mechanism is arranged in this manner the elasticity of the springs 29 is made such that at the proper load on thc shaft 25 the springs are compressed, while at a smaller load the springs expand and 30 to rotate relatively to the shaft 25 so that the disk 31 is moved laterally. A converse arrangement may, however, be used in which the strength of the springs is such that they expand at the proper load on the shaft 25, while they are compressed when the load is increased. The lateral movement of the disk 31 in the desired direction can be accomplished by providing the malescrew 32 with a left-hand or right-hand thread.

ln another modification. the projections 27 and 28 may be provided with electrical' contacts that are closed or opened when the springs 29 are lcompressed or expand. The contacts operated in this manner may be used to close or open the circuit of the electromagnet .20. When an arrangement of this kind is employed the lever mechanism 35, 36, 37 can, of course, be dispensed with.

The springs 29 may, of course, be constructed in various ways and many modifications of the entire arrangement are possible. Thus the vibrating trough may be replaced by another kind of fee ing device such as worms, feeding Wheels and the like.

An advantage of the vibrating trough over these forms of feeding devices is that it is capable of dealing with the most various kinds of materials, an-'l also with fragmentary material whose granules differ very greatly in size, without giving rise to any trouble.

An advantage that accrues from arranging the vibrating trough in the easing 9 (that is, of course, filled with dust) an'd placing the driving mechanism in a separate chamber 1() is that the driving mechanism operates in a space that is entirely free from dust. By providing the recess 18, through which the shaft 8 extends, the possibilitv is gained of attaching to this shaft the fork 7 in the chamber 10, while enabling the two shaft ends, that project into the chamber 9, to be attached to the two arms' that oseillate the trough 3. In this manner a simple and reliable drive is obtained, while the chambers 9 and 10 are entirely sepa-rated from each other. Many variations of this feature of the invention .are possible. without departing from its scope.

- In order to avoid an incessant throwing on and off of the driving mechanism of the `feeding device the mill isarranged in practice so that the torque or current strength in the driving motor circuit may decrease Aby about 1() to 20 per cent of a given value before the feeding mechanism is started. Thus to fully utilize the power of the electric motor or motors the feeding mechanism is started whenever the motor Currentsinks by 10% beneath its normal strength, while the said mechanism is only stopped again when the motor current rises by 10% above its normal value.

As the torque of the two shafts of the eddy mill are in a high degree dependent on each other, it suflices for the control of the feeding'device to measure or determine the torque of one of said shafts only. When the shafts are driven by electric motors the strength of the motor current is a measure of th-e amount of torque applied to them. According to the kind of motors used the armature current, field current or both are used as a criterion.

I claim:

`1. The combination, with a mill having a rotary shaft of the kind described, of a feeding device for introducing material to be ground into the mill, a driving member, an elastic. member for transferring the force of said driving member to sai'l rotary shaft while permittting movements of the drivmeans for affecting driving member ing member and the rotary shaft relatively to each other, and means for a'ecting said feeding device at a certain degree of relative movement between said driving member and said rotary shaft.

2. The combination, with a mill having a rotary shaft of the kind described, of a feeding' device for introducimej material to be ground into the mill, an operating.,r shaft, a coupling for transferring motion from the operating shaft to the feeding device, a driving member, an elastic member for transferring the force of said driving member to said rotary shaft while permittingr movements of the driving member and the rotary shaft relatively to each other, and

said coupling at a certain degree of relative movement between said driving member and said rotary shaft.

3. The combination, with a mill having a rotary shaft of the kind described, of a feeding device for introducing` material to be ground into the mill, an o'ierating shaft, a coupling for transferring motion from the operating shaft to the feeding device, a

driving member, anI elastic member for transferring the force of said driving member to said rotary shaft while permitting rotary movements of the driving member and the rotary shaft relatively to each other7 a threaded axially displaceable member that rotates with said driving member, a second threaded member fixed on said rotary shaft, the thread of this member being arranged to cooperate with the thread of said axially displaceablemember so that it moves axially With respect to said rotary shaft when said driving member and rotary shaft execute a rotary movement relatively to each other, and means for affecting said coupling whenever said axially displaceable member is displaced to a certain degree.

4;. The combination, With a mill having a rotary shaft of the kind described, of a feeding device for introducing material to be ground into the mill, an operating shaft, a coupling for transferring motion from the operating shaft to the feeding. device, a driving member, an elastic member for transferring the force of said driving member to said rotary shaft while permitting movements of the driving member and the rotary shaft relatively to each other, means for affecting an electric contact at a certain degree of relative movement between said and said rotary shaft, and

an electromagnet for operating said coupling when said electric contact is affected. 5. A mill of the kind described comprising a grinding chamber, a rotary member for to be ground in said chamber, a rotary shaft for driving said rotary member, an oscillatable feeding chute for introducing material into they grinding chamber, a closed chute-containing chamber, a drivingr mechanism for said chute, a separate chamber for the driving mechanism adjoining the chute-containing chamber, and a shaft for transferring motion from said driving mechanism to said chute, a part of this shaft being located in the Chute-containing chamber and another in said separate chamber.

6. A mill of the kind described comprising a grinding chamber, a rotary member for moving the material to be ground in said chamber, a rotary shaft for driving said rotary member, an oscillatable feeding chute for introducing material into the grinding chamber, a closed chute-containing chamber, a driving mechanism for said c hute, a separate chamber for the driving mechanism adjoining the chute-containing chamber, a driving means for applying a torque to said shaft, and means for starting said driving mechanism when said torque decreases to a certain extent and for stopping this mechanism when the torque has increased again to a given strength.

7. A mill of the kind described comprising. a grinding chamber, a rotary member for moving the material to be ground in said chamber, a rotary shaft for driving said rotary member, an oscillatable feeding chute for introducing material into-the grinding chamber, a closed chute-containing chamber, a driving mechanism for said chute, a separate chamber for the driving mechanism adjoining the chute-containing chamber, a shaft for transferring motion from said driving mechanism to said chute, a part of this shaft being located in the chute-containing chamber and another part being located in said separate chamber, a driving means for a plylng a torque to said shaft, and means or starting said driving mechanism When said torque decreases to a cer. tain extent and for stopping this mechanism when the torque has increased again to av given strength. j

In testimony whereof I ati'ix my signature.

ERWIN KRAMER.

part being located 

